The anaerobic/fermentation of biodegradable material is relatively well known and generally understood by those knowledgable in the art. Briefly, the exclusion of oxygen will enable methogenic bacteria to develop. Within the process of their development, methane gas, carbon dioxide, hydrogen sulfide, amnonia and other gasses are given-off from the biodegrading mass.
Prior to this invention, the state of the art had been centered around designs low in height, wider and longer than they are tall, and requiring many tubes, conduits and transfer pipes to move the mass from one area of digestion to another. Such designs require meters, dials, gauges, tubes, valves and other paraphernalia (see U.S. Pat. Nos. 2,572,767; 2,605,220; 2,772,233; 2,777,815; 2,661,332; 3,981,800; 4,046,551; 3,981,803; 4,092,338; 4,274,838; 4,057,401; 4,100,023; 4,366,059; and 4,378,437). Such designs prevent, restrict, or impede the natural volcanic action inherent in the vertical digestion processes.
It is common knowledge that as bacteria attack fresh matter fed into an anaerobic digester, carbon dioxide is formed as a by-product of this initial action. As the carbon dioxide is formed, the initial content of oxygen is consumed. This consumption of oxygen enables methogenic bacteria to propagate and develop. It is at this stage of the inherent process in anaerobic digestion that the methogenic bacteria become dominant. The methogenic bacteria, in turn, attack the material that has been freed of its oxygen content. This action by the methogenic bacteria upon biodegradable material results in the production of methane gas and other gasses.
As the methane is forming in the material being attacked by the methogenic bacteria, the material being attacked begins to rise to the surface of the mass of material contained within the digesting area, much in the same manner as a balloon filled with helium will rise into the sky until the capacity of the balloon is exceeded by the pressure of the gas expanding within due to the reduced atmospheric pressure at the higher elevation, and thereby exploding the balloon. The gasses escape and the balloon, now heavier than the atmosphere without the lighter-weight gas, falls back to the surface. So, too, does the material being attacked by methogenic bacteria. As the gas expands within the cellular structure of the biodegradable material, the mass begins to rise from the bottom of the digester, due to the fact that the molecular weight of methane is only 0.553 and, therefore, lighter than the surrounding material. When the expanded volume of the methane gas within the cellular structure reaches the point at which the cellular structure can no longer retain the expanding gas, the cellular structure literally explodes, thereby releasing the methane gas and other gasses, and allowing the cellular structure to fall to the floor of the digester. This action continues until the biodegradable material is unable to provide the methogenic bacteria with biodegradable elements to act upon in the methogenic process.
The prior art (see list of patents, above) with its use of tubes and recirculating gas jets, does not allow this natural volcanic action to take place to the fullest extent it is capable and the action is further restricted by low, wide and long designs as are illustrated and described.
Another problem inherent in the prior art is that anaerobic fermentation/digestion unalterably creates `scum`. . . a slimy, adhering, accumulation of bacterial plaque . . . which is a natural by-product of the inherent action. This scum will adhere to most surfaces with which it comes in contact. Therefore, a problem not solved by prior inventions is the clogging of designed jets, tubes and internal heating pipes and conduits, and the coating of said heating pipes, tubes, and conduits, thereby reducing their design efficiency.
Whenever there is a pipe, conduit or transfer channel for the purpose of agitation, transferring of material or interior heating, there is inherently a cause for maintenance, a reduction in operating efficiency, and the inevitable cost, shutdown, lowering of operating efficiency and reduction in production. Pipes, conduits, and channels clogging in an anaerobic digester/fermentation tank eventually lead to the system being shut down to repair, replace, or adjust the system to restore it to its designed efficiency. Such a shutdown of activity results in a loss of production and a mandatory interruption in the process.
Another problem exists in the prior designs for single area digesters (U.S. Pat. Nos. 2,605,220; 2,772,233; 3,981,803; 4,092,338; 4,100,023; 4,233,155; and 4,274,838), in that none has incorporated a means to deflect incoming material away from the exit channel, thus allowing undigested material to be prematurely expelled from the digester.
A further problem of prior digesters has been the need for intensive management. The overabundance of valves, dials, guages, switches, transfers and operating paraphernalia demand constant observation and attention. Prior U.S. Pat. Nos. 2,572,767; 2,605,220; 2,661,332; 3,981,800; 4,406,551; 4,057,401; 4,100,203; 4,233,155; and 4,366,059 have been predicted upon the attempt to control some segment of the process, and therefore, those designs tend to complicate the apparatus and the process making it mandatory to specifically manage the process. The flaw in such a requirement is that if one step is delayed, or accellerated, the entire process is interrupted until a specific management step is initiated. This is most prevalent in designs that require more than one area of activity/processing.
In actuality, the entire process of anaerobic digestion and the production of methane gas and other gasses from such action is interdependent upon sequentially related factors. Any attempt to interfere with the natural progression of bacterial action will only delay, or stop, the object of the invention. At the very least, a guarantee of less than maximum potential is effected in systems so designed.
A further problem in all prior state of the art systems is that they have no designed means to exactly control the amount of new material fed into the system, as it relates to the volume of the system, without an excessive amount of technologically advanced, on-site management and/or additional expensive equipment and operating paraphernalia that is subject to breakdown, maintenance and repair/replacement, with attending cost and reduction in efficiency. This failure in the prior art virtually eliminates the use of such systems by people not skilled in such control management for the production of beneficial gasses or the object for which they were invented.
A further problem in the prior art has been inability to retain the material for a sufficient period of time to eliminate unwanted aerobic pathogens and viruses. Such a benefit would enable the material used for digestion to include human excrement found in municipal sewage systems, without fear of spreading disease, and would include the benefit of effectively sterilizing the digested residue against the passage of live insect larva, aerobic disease pathogens and viruses, all of which are present where digester material is accumulated for processing. Without a means to deflect freshly added material away from the point at which said material is to pass out of the digester, no assurance is given that the material will be retained long enough in the digesting area to rid the substance of aerobic pathogens and viruses.
Further, no enhancing of the fertilizer value will be effected. Because of the inherent process of anaerobic digestion, the residue (the material expelled from the digester about it has been subjected to the complete anaerobic process), if retained in the process long enough, will be changed to a more beneficial pH, and have more available nitrogen and more available potassium for the fertilization of plant life.